1. Field of the Invention
The present invention relates to an image processing method and an image sensing device, and particularly relates to an image processing method and an image sensing device which can maintain a constant offset for the correlation window.
2. Description of the Prior Art
Conventionally, an image sensor in an optical mouse always utilizes a correlation window (ex. a 3×3 or 5×5 correlation window) to detect the displacement of the optical mouse. Also, the image sensor with a constant frame rate or “pre-programmed” variable frame rates will use “prediction” to estimate a next “offset” location for the correlation window. The offset indicates a difference between starting coordinates for correlation windows at different timings. For example, each correlation window is supposed to have a starting coordinate of (0.0). However, the correlation window may start at a different coordinate such as (1,1) due to the movement of the optical mouse.
The above-mentioned “prediction” may be non-efficient to predict the offset if the optical mouse is operating at some specific situations, for example, at a low speed but a high frame rate.